The present invention relates to crane grabs for digging loose material such as earth or sand. More particularly the invention relates to grabs of the kind adapted to be operated by a single crane wire only, i.e. grabs which are operable by means of simple cranes such as ordinary building cranes having a single hoist wire only. It has already been suggested to provide a grab for this purpose with manually operable selector means shiftable between a position, in which the open grab will be closed for digging in response to the crane wire being hoisted, and a position in which the grab is allowed to open itself when it has been placed on the ground and is thereafter lifted again. Of course, it is an advantage that the grab may be used in connection with an ordinary building crane, but it is disadvantageous that in operation the grab will require the assistance of an additional operator for operating the selector means on the ground.